Metal nanoparticles stabilized with derivatized polyethyleneimines or polyvinylamines

ABSTRACT

The invention relates to metal nanoparticles and a process for the preparation thereof, in which a metal salt solution is reduced with a reducing agent in the presence of the derivatized polyethyleneimines or polyvinylamines. Metal salt solutions of two or more different metals can be reduced simultaneously or in succession, metal nanoparticles comprising two or more different metals being obtained. Preferred metals are silver, palladium, and platinum. Suitable reducing agents are, for example, formic acid, formaldehyde, diethanolamine, 5-pentenoic acid and sodium borohydride. Silver can be used in the form of silver oxide and/or silver nitrate, palladium in the form of alkali metal tetrachloropalladate or palladium(II) nitrate and platinum in the form of alkali metal tetrachloroplatinate or tetraamineplatinum(II) nitrate.

The invention relates to metal nanoparticles stabilized with derivatized polyethyleneimines or polyvinylamines.

The usefulness of metallic nanoparticles in various applications, for example in fibers, coating materials, films, binders, adhesives and resins, is documented by numerous publications. Metallic nanoparticles can be used as catalysts or in printing inks, as precursors for the printing of electronic circuits or for soldering, or they are used because of their special optical, photonic, magnetic or chemical properties. Silver nanoparticles are additionally known for their ability to free aqueous solutions from harmful microorganisms. Silver nanoparticles bound to biotin are known to be a highly sensitive sensor.

A principal problem associated with the use of metal nanoparticles is the inherent instability thereof, which leads to coagulation and finally to precipitation of dendritic metal particles which are substantially larger than 100 nm. This is also disadvantageous for the applications described above in that the nanodisperse system has the highest efficiency, and agglomeration, for example, reduces the catalytic activity or the biocidal action or leads to an increase in the sintering temperature during use in printing inks. It is moreover desirable for all nanoparticles to be in contact with the surrounding medium so that they can display their full efficiency.

It is known that metal nanoparticles can be stabilized to agglomeration and precipitation from liquid media.

A. Dawn et al., Langmuir 2007, 23, 5231 to 5237, describe the preparation of monodisperse silver nanoparticles in the presence of poly-o-methoxyaniline (POMA) as a reducing and stabilizing polymer. There, an aqueous silver nitrate solution is added to a solution of POMA in chloroform, and the silver nanoparticles form at the phase boundary. Depending on the duration of aging (from 8 to 21 days), nanoparticles having a mean diameter of from 12.0 to 21.9 nm are formed. Only very dilute solutions of POMA and silver nitrate are used.

T. Sato et al., Macromol. Mat. Eng. 2006, 291, pages 162 to 172, describe the preparation of copolymer-stabilized silver nanoparticles by addition of a methanolic silver nitrate solution to a solution of divinylbenzene-ethyl acrylate copolymer in tetrahydrofuran and reduction with NaBH₄. The reaction mixture is finally added to methanol and the precipitated silver-containing copolymer is isolated.

J. H. Yeum et al., Fibers and Polymers 2005, vol. 6, No. 4, pages 277 to 283, describe the preparation of PMMA/silver nanocomposite microspheres by suspension polymerization of methyl methacrylate in the presence of silver nanoparticles and polyvinyl alcohol as a suspending aid. Commercially available aqueous dispersions of silver nanoparticles having diameters of from about 15 to 30 nm are used.

J.-W. Kim et al., Polymer 45, 2004, pages 4741 to 4747, describe the deposition of colloidal silver on microspheres of ethylene glycol dimethacrylate/acrylonitrile copolymer which are prepared by suspension polymerization. An aqueous silver nitrate solution is added to the aqueous copolymer solution and reduced with aqueous hydrazine solution. Porous microspheres having particle diameters in the region of microns, which comprise the silver nanoparticles with diameters in the range from 10 to 50 nm on the inner and outer surface, are obtained. Antibacterial action of the microspheres is also investigated.

Y. Lu et al., Polymeric Materials: Science & Engineering 2006, 94, pages 264-265, describe metallic nanoparticles which are embedded in the polymeric network of a core/shell particle. The colloidal core consists of polystyrene and the shell consists of poly(N-isopropylacrylamide) which is crosslinked by N,N′-methylbisacrylamide. The core/shell particles comprise 10.4% by weight of silver nanoparticles in a size of 8.5+/−1.5 nm. The silver nanoparticles are prepared by reduction of silver nitrate in an aqueous suspension, which comprises the core/shell particles, with sodium borohydride.

A. Gautam et al., Synthetic Metals, 157 (2007), pages 5 to 10, describe the preparation of silver nanoparticles having a particle size in the range from 10 to 30 nm. There, an aqueous silver nitrate solution is reduced with polyvinyl alcohol (PVA), PVA simultaneously stabilizing the nanoparticles formed. The silver-PVA nanocolloid solution is allowed to age at from 2 to 5° C. for from 30 to 50 hours, heated and poured to give thin layers from 1 to 5 mm thick. After the polymer has been burnt off at from 300 to 400° C. in air, a finely divided powder of silver nanoparticles remains. At silver concentrations >5% by weight, agglomeration of the primary particles occurs.

Silver nanoparticles can also be formed by reduction of silver cations in the presence of polyvinylpyrrolidone (PVP) with sodium borohydride, citric acid or sodium citrate, as described in Karpov et al., Colloid Journal 2007, vol. 69, pages 170 to 179, and the literature cited therein.

WO 2005/077329 describes a process in which silver nanoparticles are deposited on the surface of porous polymer particles. The polymer particles are produced by emulsion polymerization in the presence of an emulsifier and stabilizer, preferably gelatin, starch, hydroethylcellulose, carboxymethylcellulose, polyvinylpyrrolidone, polyvinyl alkyl ether, polyvinyl alcohol or polydimethylsiloxane/polystyrene block copolymer. The silver nanoparticles are then deposited by reduction of silver salts, for example with hydrazine, LiAlBH₄, NaBH₄ or ethylene oxide. The silver/polymer composite nanospheres are used in cosmetic compositions.

C.-C. Chen et al., Langmuir 2007, 23, pages 6801 to 6806, describe the preparation of gold nanoparticles using alkylated polyethyleneimines as reducing agents and stabilizers, a commercially available linear polyethyleneimine alkylated with 1,2-epoxydecane being used. The gold particles are prepared by reduction of metal ions, which are present in the form of an aqueous HAuCl₄ solution, by stirring at room temperature. The alkylated polyethyleneimine which is oxidatively dealkylated acts as a reducing agent and at the same time as a stabilizer for the gold nanoparticles formed.

WO 2004/086044 describes silver nanoparticles bound to biotin as a highly sensitive sensor.

DE 10 2006 017 696 A1 describes a process for the preparation of metal particles sols having a metal particle content of ≧1 g/l, in which a metal salt solution is reacted with a solution which contains hydroxide ions and is prepared by dissolving bases, such as LION, NaOH, KOH, aliphatic or aromatic amines, in water, and the solution obtained is reduced with a reducing agent in the presence of a dispersant which stabilizes the particles formed.

W. J. Liang et al., J. Col. Interf. Sci. 2006, 294(2), 371-375 describe the use of polyethyleneimine/polyoxypropylenediamine copolymer for the preparation of platinum nanoparticles. The stabilizing effect is based on the formation of spherical polymer micelles, which is brought about by the addition of H₂PtCl₆. The reduced Pt (0) particles are enclosed in the polyethyleneimine block on the outside of the micelles, which surrounds the polyoxypropylene block.

The processes of the prior art as a rule lead to systems in which the metal nanoparticles are embedded in the polymer particles and hence cannot display their special properties. Examples of such specific properties are macroscopic conductivity, the biocidal activity, the optical resonance, the magnetic properties, the catalytic properties and the ability to sinter together with formation of conductive structures of the metal nanoparticles. Furthermore, many of the processes of the prior art are complicated and comprise multistage syntheses and/or ingenious purification procedures in order to obtain the end product. Furthermore, only a low concentration of metal nanoparticles is obtained with many processes of the prior art.

It is an object of the present invention to provide a process for the preparation of metal nanoparticles which is suitable for the preparation of highly concentrated aqueous solutions of metal nanoparticles, in particular of silver, platinum and palladium nanoparticles, without agglomeration of the metal nanoparticles occurring.

The object is achieved by metal nanoparticles stabilized with derivatized polyethyleneimines or polyvinylamines and a process for the preparation thereof in which a metal salt solution is reduced with a reducing agent in the presence of the derivatized polyethyleneimines or polyvinylamines.

Suitable polyethyleneimines or polyvinylamines whose derivatives can be used according to the invention are described below under A to F.

A Homopolymers of Ethyleneimine (Aziridine)

Polyethyleneimines which may be used are polyethyleneimine homopolymers which may be present in uncrosslinked or crosslinked form. The polyethyleneimine homopolymers can be prepared by known processes, as described, for example, in Römpps Chemie Lexikon, 8th edition, 1992, pages 3532-3533, or in Ullmanns Enzyklopädie der Technischen Chemie, 4th edition, 1974, vol. 8, pages 212-213, and the literature stated there. They have a molecular weight in the range from about 200 to 1 000 000 g/mol. Corresponding commercial products are available under the name Lupasol® from BASF SE or under the name Epomin® from Nippon Shokubai.

B Graft Polymers of Polyamidoamines with Ethyleneimine

In the context of the present invention, polyethyleneimines are also those polymers which comprise ethyleneimine units and are obtainable by grafting polyamidoamines with ethyleneimine. These may be crosslinked with the crosslinking agents mentioned under A.

Grafted polyamidoamines are disclosed, for example, in U.S. Pat. No. 4,144,123 or DE-B-24 34 816. The polyamidoamines are obtainable, for example, by condensation of

-   (i) Polyalkylenepolyamines, which may be present as a mixture with     diamines, with -   (ii) at least dibasic carboxylic acids, such as oxalic acid, malonic     acid, succinic acid, maleic acid, fumaric acid, itaconic acid,     adipic acid, tartaric acid, citric acid, propanetricarboxylic acid,     butanetetracarboxylic acid, glutaric acid, suberic acid, sebacic     acid, terephthalic acid and the esters, acid chlorides or anhydrides     thereof, which may be present as a mixture with up to 50 mol % of     monobasic amino acids, monobasic hydroxycarboxylic acids and/or     monobasic carboxylic acids,     in a molar ratio of (i) to (ii) of from 1:0.5 to 1:2.

Polyalkylenepolyamines are understood as meaning compounds which comprise at least 3 basic nitrogen atoms in the molecule, for example diethylenetriamine, dipropylenetriamine, triethylenetetramine, tripropylenetetramine, tetraethylenepentamine, pentaethylenehexamine, N-(2-aminoethyl)-1,3-propanediamine and N,N′-bis(3-aminopropyl)ethylenediamine.

Suitable diamines are, for example, 1,2-diaminoethane, 1,3-diaminopropane, 1,4-diaminobutane, 1,6-diaminohexane, 1,8-diaminooctane, isophoronediamine, 4,4′-diaminodiphenylmethane, 1,4-bis(3-aminopropyl)piperazine, 4,9-dioxadodecane-1,12-diamine, 4,7,10-trioxamidecane-1,13-diamine or a,z-diamino compounds of polyalkylene oxides.

The condensation of the compounds (i) and (ii) is effected as described, for example, in EP-B 0 703 972.

The graft polymers comprise in general from 10 to 90% by weight of polyamidoamines as grafting base and from 90 to 10% by weight of ethyleneimine as a graft.

C Graft Polymers of Polyvinylamines with Ethyleneimine

In the context of the present invention, polyethyleneimines are also those polymers comprising ethyleneimine units which are obtainable by grafting polyvinylamines with ethyleneimine or oligomers of ethyleneimine. Polyvinylamines are obtainable by complete or partial hydrolysis of polymers of open-chain N-vinylcarboxamides of the general formula (I)

where R¹, R²═H or C₁- to C₆-alkyl, and are described in more detail under E and F (see below). The degree of hydrolysis is in general from 5 to 100%. The graft polymers may be crosslinked.

The graft polymers comprise in general from 10 to 90% by weight of polyvinylamines as a grafting base and from 90 to 10% by weight of ethyleneimine as a graft.

D Polymers of the Higher Homologs of Ethyleneimine

In the context of the present invention, polyethyleneimines are also understood as meaning those polymers of higher homologs of ethyleneimine, such as propyleneimine (2-methylaziridine), 1- or 2-butyleneimine(2-ethylaziridine or 2,3-dimethylaziridine), which correspond to the compounds mentioned under A to C. However, the polymers of ethyleneimine are preferred.

E At Least Partly Hydrolyzed N-vinylcarboxamide Homopolymers

Polyvinylamines are at least partly hydrolyzed N-vinylcarboxamide homopolymers. Their preparations are, for example, from open-chain N-vinylcarboxamides of the above formula (I). Suitable monomers are, for example, N-vinylformamide (R¹═R²═H in formula I), N-vinyl-N-methylformamide (R¹=methyl, R²═H in formula I), N-vinylacetamide (R¹═H, R²=methyl in formula I), N-vinyl-N-methylacetamide (R¹═R²=methyl in formula I) and N-vinyl-N-ethylacetamide (R¹=ethyl, R²=methyl in formula I). N-vinylformamide is preferred.

F At Least Partly Hydrolyzed N-vinylcarboxamide Copolymers

In the context of the invention, polyvinylamines are also the copolymers of (a) from 0.1 to 100 mol % of N-vinylcarboxamides of the formula (I) and (b) from 0 to 99.9 mol % of vinyl formate, vinyl acetate, vinyl propionate, vinyl alcohol, N-vinylurea, N-vinylpyrrolidone, N-vinylpiperidone, N-vinylcaprolactam, N,N-divinylethyleneurea and/or N-vinylimidazole, the sum of (a) and (b) being 100 mol %, which are at least partly hydrolyzed.

Preferred polyethyleneimines, the derivatives of which are used according to the invention, are the homopolymers of ethyleneimine which are described under A and the graft polymers of polyamidoamines with ethyleneimine which are described under B. Preferred polyethyleneimines and graft polymers of polyamidoamines with ethyleneimine are those having a molecular weight in the range from 500 to 2 000 000 g/mol, particularly preferably from 1000 to 100 000 g/mol, in particular from 5000 to 50 000 g/mol.

The polyethyleneimines or polyvinylamines mentioned under A to F are derivatized at the reactive nitrogen atoms by

(1) 1,4-Addition (Michael addition) onto alpha,beta-unsaturated carbonyl compounds. Suitable alpha,beta-unsaturated carbonyl compounds are acrylic acid and acrylates, for example alkyl acrylates and hydroxyalkyl acrylates, methacrylic acid and methacrylates, for example alkyl methacrylates and hydroxyalkyl methacrylates, acrolein, arylamides and acrylonitrile;

(2) Reaction the compounds capable of nucleophilic substitution by the imine nitrogen, preferably with hydrocarbon compounds, in particular alkyl compounds or alkylene compounds, which have one or two suitable leaving groups, for example acetate, brosylate, mesylate, nosylate, tosylate, trifluoroacetate, trifluorosulfonate, chlorine, bromine or iodine; examples are organic and inorganic halides, in particular alkyl halides, alkyl trifluoroacetates, alkyl (bromo)toluenesulfonates and alkyl phenolates, such as methyl chloride, methyl trifluoroacetate, trimethylsilyl chloride and methyl bromotoluenesulfonate; and dihaloalkanes, such as 1,2-dichloroethane, 1,3-dichloropropane, 1,4-dichlorobutane and 1,6-dichlorohexane;

(3) Reaction with dialdehydes and/or diketones; suitable dialdehydes and diketones are, for example, glyoxal and 1,3-pentanedione;

(4) Reaction with epoxides, diepoxides, halohydrin ethers and/or bishalohydrin ethers; suitable diepoxides are, for example, 1,6-hexanediol bisglycidyl ether and bisglycidyl ethers of oligo- and polyethylene glycols; and reaction products of halohydrins, for example epichlorohydrin, with alkylene glycols and polyalkylene glycols having 2 to 100 ethylene oxide or propylene oxide units;

(5) Reaction with alkylene carbonates, for example ethylene carbonate or propylene carbonate, and bischloroformates, for example 2,2-dimethylpropylene bischloroformate;

(6) Reaction with polyalkylene glycol ethers;

(7) Reaction with carboxylic acids and carboxylic esters in an amidation reaction;

(8) Reaction with isocyanates; for example with diisocyanates, such as hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane 4,4′-diisocyanate and diphenylmethane diisocyanate;

(9) Reaction with formaldehyde and cyanide salts in a Strecker reaction;

(10) Reaction with formaldehyde and further reaction of the resulting imines with further components by Strecker reaction, Mannich reaction or Eschweiler-Clarke reaction, carboxymethylation or phosphonomethylation.

A plurality of derivatizing reactions may be combined with one another. Relatively high molecular weight polymers are obtained by crosslinking with polyfunctional compounds.

Preferred derivatization reactions are

-   (1) 1,4-Addition (Michael addition) onto alpha,beta-unsaturated     carbonyl compounds; -   (4) Reaction with diepoxides; -   (8) Reaction with carboxylic acids or carboxylic esters.

In a special embodiment, polyethyleneimines A are reacted with a diepoxide and/or bischlorohydrin ether and then reacted with one or more alpha,beta-unsaturated carbonyl compounds; for example, they are reacted with 1,6-hexanediol bisglycidyl ether or bisglycidyl ether of a polyalkylene glycol and then with (meth)acrylic acid, alkyl (meth)acrylate, for example methyl acrylate, and/or hydroxyalkyl (meth)acrylate, for example hydroxyethyl acrylate or 4-hydroxybutyl acrylate.

Preferred alkyl (meth)acrylates are the C₁-C₆-alkyl (meth)acrylates; preferred hydroxyalkyl (meth)acrylates are the hydroxy-C₁-C₆-alkyl (meth)acrylates.

In a further special embodiment, polyethyleneimines A are reacted with a diepoxide and/or bischlorohydrin ether and then with a carboxylic ester, for example ethyl acetate.

In a further special embodiment, polyethyleneimines A are reacted with acrylic acid, hydroxyalkyl acrylates, for example hydroxyethyl acrylate or 4-hydroxybutyl acrylate, and/or acrylamides, for example N-tert-butylacrylamide or N-isopropylacrylamide or other N-substituted acrylamides.

Preferred acrylamides are the N—C₁-C₆-alkylacrylamides.

In a further special embodiment, polyamidoamines B are reacted with acrylic acid.

In a further special embodiment, polyamidoamines B are reacted with a diepoxide and/or bischlorohydrin ether, for example the bisglycidyl ether of a polyalkylene glycol, and then with acrylic acid.

The derivatization of the polyalkyleneimines is carried out in general at temperatures of from −30° C. to 300° C. in the gas phase, if appropriate under pressure, or in solution. The derivatization is preferably carried out in the same medium in which the preparation of the nanoparticles is also effected. It is preferably carried out at temperatures of from 50 to 150° C., in particular from 75 to 95° C. Preferred reaction medium is water.

The metal nanoparticles are generally prepared by reduction of the corresponding metal salts with a reducing agent in the presence of the derivatized polyalkyleneimines or polyvinylamines. Suitable reducing agents may be organic or inorganic reducing agents. Examples are alcohols, such as methanol or ethanol, amino alcohols, such as 1,2-aminoethanol, diethanolamine, aldehydes, such as formaldehyde or acetaldehyde, ketones, carboxylic acids, such as formic acid, acetic acid or oxalic acid, alkenoic acids, such as 5-pentenoic acid, hydrazine or hydrazine derivatives, azo compounds, such as AIBN (azobisisobutyronitrile), carboxylic anhydrides, amides, amines, ethers, esters, alkenes, dienes, thio compounds, mono- or polysaccharides, phosphorus or arsenic derivatives, hydrogen or oxides of carbon. Suitable inorganic reducing agents are hydrogen, metals, such as zinc, calcium and magnesium, and metal hydrides, such as sodium borohydride, and furthermore Sn(II) salts, Fe(II) salts, thiosulfates, thiosulfites, phosphites, phosphanes, sulfides and disulfides.

Formic acid, formaldehyde, diethanolamine, methanol, ethanol, 5-pentenoic acid, ascorbic acid, citric acid, lactic acid, oxalic acid, glucose, fructose and sodium borohydride are preferred. Particularly preferred organic reducing agents are formic acid or formaldehyde. Carbon dioxide forms thereby and can be easily removed from the reaction mixture. For example, carbon dioxide can be removed from the reaction mixture by stripping with air. Furthermore, diethanolamine, 5-pentenoic acid, ascorbic acid and citric acid are particularly preferred. Furthermore, ethanol, methanol, ethylene glycol, diethylene glycol, hydrazine and oxalic acid are preferred.

Preferred inorganic reducing agents are sodium borohydride, Sn(II) salts, Fe(II) salts, thiosulfates, thiosulfites, phosphites, phosphanes, sulfides and disulfides.

In an embodiment of the process according to the invention, an alcohol is used both as a solvent and as a reducing agent. Apart from the alcohol, no further reducing agent is used. This method is described in principle in Atf. Funct. Mater. 2003, 13 No. 2: Synthesis of nanoscaled ZnO particles by thermolysis of metal salt precursor in diethylene glycol; J. Mater. Res. Vol. 10, No. 1: Synthesis of spherical ZnO nano particles by the hydrolysis of Zn-acetate in diethylene glycol; J. Sol-Gel Sci. Techn. 2004, 29, 71-79: Synthesis of monodispers ZnO-spheres with diameter of 5-10 nm via heating of Zn-acetate in methanol, ethanol and 2-methoxyethanol. In contrast to the processes described there, the reduction is carried out according to the invention in the presence of derivatized polyethyleneimines or polyvinylamines as additional stabilizers.

The metal nanoparticles are generally prepared by reduction at temperatures of from −30 to 300° C. and pressures of from 10 mbar to 100 bar, preferably at temperatures of from 0 to 100° C., particularly preferably from 20 to 95° C. Atmospheric pressure is preferably employed, so that special vacuum apparatuses or pressurized containers are not required.

For example, the temperature of the reduction of the metal salt solution can be chosen so that the reaction is complete after 24 hours at the latest, but preferably is complete after 10 hours at the latest and in particular after 5 hours at the latest. For example, this temperature may be from 30 to 50° C. in the case of silver as the metal and formic acid as the reducing agent.

The metal nanoparticles stabilized according to the invention may consist of copper, silver, gold, palladium, nickel, platinum, rhodium, iron, bismuth, iridium, ruthenium or rhenium or of two or more of these metals. These metals may be present in the form of their oxides, nitrates, phosphates, sulfates, sulfites, phosphonites, nitrites, borates, aluminates, silicates, cyanides, isocyanates, thioisocyanates, halides, perchlorates, periodates, perbromates, chlorates, iodates, bromates, hypochlorites or in the form of complex compounds. Examples of suitable complex compounds are silver-ammonia complexes, diaminodichloropalladate, tetrachloropalladate or tetrachloroplatinate. It is also possible to use salts of a plurality of different metals, which can be reduced simultaneously or in succession.

Preferred metals are copper, silver, gold, nickel, palladium, platinum, cobalt, rhodium, iridium, iron, ruthenium and osmium. Copper, silver, palladium and platinum are particularly preferred. Silver is used, for example, in the form of silver oxide, silver acetate, silver nitrate or a silver oxide/silver nitrate mixture, palladium as alkali metal tetrachloropalladate, palladium(II) nitrate, palladium(II) acetate, tetraminopalladium(II) nitrate, ammoniumhexachloropalladate(IV), diaminopalladium(II) chloride, bis(triphenyl-phosphine)palladium(II) chloride, bis(2,4-pentanedionato)palladium(II), 1,2-bis-(diphenylphosphino)ethanepalladium(II) chloride, bistriphenylphosphinepalladium(II) chloride, platinum as alkali metal tetrachloroplatinate, bis(2,4-pentanedionato)platinum(II), hexachloroplatinic(IV) acid hydrate, tetraamineplatinum(II) chloride, platinum(IV) nitrate, tetraamineplatinum(II) nitrate, platinum(II) acetate, and rhodium as hexachlororhodic(III) acid, rhodium(III) acetate, rhodium(III) oxyhydrate, chlorotris(triphenyl)phosphinerhodium(I) or acetylacetonato(cyclooctadiene)rhodium(I).

The reduction can be carried out in organic solvents, such as alcohols, polyols, esters, chlorohydrocarbons, phenols, DMSO, DMF, NMP and ethers, such as THF, dioxane or dioxolane. Other reaction media are also conceivable, such as salt melts or ionic liquids. Water or aqueous organic solvent mixtures, glycol and diethylene glycol are preferred solvent, and water and aqueous organic solvent mixtures are particularly preferred.

If the reduction is carried out in an alcohol, the alcohol may act as a reducing agent. Suitable monohydric alcohols are ethanol, methanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, tert-butanol, n-pentanol, isopentanol, 2-methylbutanol, sec-pentanol, tert-pentanol, 3-methoxybutanol, n-hexanol, 3-methylpentanol, sec-hexanol, 2-ethylbutanol, sec-heptanol, 3-heptanol, n-octanol, 2-ethylhexanol, sec-octanol, n-nonyl alcohol, 2,6-dimethylheptan-4-ol, n-decanol, sec-undecyl alcohol, trimethylnonyl alcohol, sec-tetradecyl alcohol, sec-heptadecyl alcohol, phenol, cyclohexanol, methylcyclohexanol, 3,3,5-trimethylcyclohexanol, benzyl alcohol and diacetone alcohol. Preferred monohydric alcohols are selected from glycol ethers, such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, ethylene glycol monophenyl ether, ethylene glycol mono-2-ethylbutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monohexyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether and dipropylene glycol monopropyl ether.

Polyhydric alcohols, for example diols, which are preferably selected from the group consisting of 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 2,3-butanediol, 1,4-butanediol, but-2-ene-1,4-diol, 1,2-pentanediol, 1,5-pentanediol, 2,4-pentanediol, 2-methyl-2,4-pentanediol, 1,2-hexanediol, 1,6-hexanediol, 2,5-hexanediol, 2,4-heptanediol, 2-ethyl-1,3-hexanediol, octanediol, 1,10-decanediol, 1,2-dodecanediol, 1,12-dodecanediol, neopentyl glycol, 3-methylpentane-1,5-diol, 2,5-dimethyl-1,3-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, 1,2-cyclohexanediol, 1,4-cyclohexanediol, 1,4-bis(hydroxymethyl)cyclohexane, mononeopentyl glycol hydroxypivalate, 2,2-bis(4-hydroxyphenyl)propane, 2,2-bis[4-(2-hydroxypropyl)phenyl]propane, diethylene glycol, dipropylene glycol, triethylene glycol, tetraethylene glycol, tripropylene glycol, tetrapropylene glycol, 3-thiopentane-1,5-diol, polyethylene glycols, polypropylene glycols and polytetrahydrofuran having a molecular weight of from 200 to 10 000, diols based on block copolymers, such as ethylene oxide/propylene oxide copolymers or polymers containing ethylene oxide or propylene oxide groups, are preferred.

Suitable diols are furthermore polyether homopolymers having an OH functionality, such as polyethylene glycol, polypropylene glycol and polybutylene glycol, binary copolymers, such as ethylene glycol/propylene glycol and ethylene glycol/butylene glycol copolymers, straight-chain ternary copolymers, such as ethylene glycol/propylene glycol/ethylene glycol, propylene glycol/ethylene glycol/propylene glycol and ethylene glycol/butylene glycol/ethylene glycol copolymers. Suitable diols are furthermore polyether block copolymers having an OH functionality, such as binary block copolymers, such as polyethylene glycol/polypropylene glycol and polyethylene glycol/polybutylene glycol, straight-chain ternary block copolymers having alkyl chains, such as polyethylene glycol/polypropylene glycol/polyethylene glycol, polypropylene glycol/polyethylene glycol/polypropylene glycol and polyethylene glycol/polybutylene glycol/polyethylene glycol terpolymers. Further suitable polyethers are described in DE 102 97 544, paragraphs [0039] to [0046].

The use of polyhydric alcohols having fewer than 10 carbon atoms is particularly preferred, in particular of those which are liquid at 25° C. and 1013 mbar, for example ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, pentanediol, hexanediol and octanediol, with ethylene glycol and 1,2-propanediol being particularly preferred.

Suitable polyhydric alcohols are furthermore triols, for example 1,1,1-Tris(hydroxymethyl)ethane, 1,1,1-Tris-(hydroxymethyl)propane, 2-ethyl-2-hydroxymethyl-1,3-propanediol, 1,2,6-hexanetriol, 1,2,3-hexanetriol and 1,2,4-butanetriol.

Furthermore, sugar alcohols, such as glycerol, threitol, erythritol, pentaerythritol and pentitol, can be used.

The derivatization of the polyethyleneimines or polyvinylamines and the preparation of the nanoparticles can be carried out as a so-called one-pot reaction without isolation of intermediates in one and the same reaction medium. First, the polyethyleneimine or polyvinylamine is derivatized by reaction with the derivatizing agent or agents, and the metal nanoparticles are then generated by addition of metal salt and reducing agent in the presence of the derivatized polyethyleneimines or polyvinylamines. It is also possible to reduce metal salt solutions of two or more different metals simultaneously or in succession, metal nanoparticles comprising two or more different metals being obtained. Successive reaction steps with different reducing agents can be carried out thereby.

The invention is explained in more detail by the examples below.

EXAMPLES Characterization

The metal nanoparticles prepared below were characterized as follows:

UV-vis spectra were recorded from 200 to 800 nm using a Hewlett-Packard 8453 spectrometer in the absorption mode in 1 cm glass cells, a suitable dilution being chosen.

Transmission electron micrographs were generated using an FEI CM120 apparatus which was operated at 100 kN, and the result was recorded using a Bioscan digital camera from Gatan.

DLS (dynamic light scattering) spectra were recorded using a ZetasizerNano S apparatus from Malvern at 23° C. and at an angle of 173°. The evaluation of the measured data was effected according to ISO Standard 13321:1996 E. The autocorrelation function obtained was logarithmatized and approximated with a third-order polynomial. The mean z value was calculated from the quadratic coefficients using temperature, viscosity, refractive index and laser light wavelength as constants in the Stokes-Einstein relationship. The distribution was calculated using the Malvern software (CONTIN procedure of S. Provencher).

Synthesis of the Polyethyleneimine Derivatives

Derivatives were prepared starting from polyethyleneimine having a weight average molecular weight M_(w) of 25 000 g/mol. The synthesis of the derivatives was effected in aqueous solution. The determination of the conversions was effected by means of NMR spectroscopy, HPLC, GC (methacrylic acid and the esters thereof) and the Preussmann test (Epoxides; R. Preussmann, Arzneimittel-Forschung 1969, 19, pages 1059 to 1073). The characterization of the products was effected by determination of the K value of 1% strength by weight solutions according to Fikentscher (H. Fikentscher, Cellulosechemie 1932, 13, pages 58 to 64). For the determination of the solids contents (SC), the samples were dried for 2 hours at 120° C. under reduced pressure. The yields are based on the amounts of substance used.

Example 1

750 g of a 56% strength aqueous solution of polyethyleneimine (M_(w)=25 000) are initially taken in a four-necked flask having an intensive stirrer and reflux condenser and are heated to an internal temperature of 95° C. with stirring. Air is passed in continuously in the process. When the temperature of 95° C. has been reached, 280.8 g of acrylic acid are added dropwise in the course of 2 hours. At the same time, 280.8 g of demineralized water are added dropwise in 2 hours. Thereafter, the experiment is stirred for a further 6 hours at 95° C. The experiment is cooled to 80° C. and diluted with a further 200 ml of water. The product is a yellow, clear solution. The K value is 27.9; solids content (SC): 42%; yield: 99%.

Example 2

150 g of a 56% strength aqueous solution of polyethyleneimine (M_(w)=25 000) and 202.3 g of demineralized water are initially taken in a four-necked flask having an intensive stirrer and reflux condenser and are heated to an internal temperature of 95° C. with stirring. Air is passed in continuously in the process. When the temperature of 95° C. has been reached, 70.3 g of acrylic acid are added dropwise in the course of 2 hours. At the same time, 280.8 g of demineralized water are added dropwise in 2 hours. Thereafter, the experiment is stirred for a further 6 hours at 95° C. The product is a light yellow, viscous solution. The K value is 17.65 (1% strength in H₂O); conversion: 100%; SC: 37.7%.

Example 3

150 g of a 24.9% strength aqueous solution of polyethyleneimine (M_(w)=25 000, crosslinked with 4.55% of bisglycidyl ether of a polyethylene glycol having an average molar mass of 2000) and 202.3 g of demineralized water are initially taken in a four-necked flask having an intensive stirrer and reflux condenser and are heated to an internal temperature of 95° C. with stirring. Air is passed in continuously in the process. When the temperature of 95° C. has been reached, 66.5 g of acrylic acid are added dropwise in the course of 2 hours. Thereafter, the experiment is stirred for a further 6 hours at 95° C. The product is a light yellow, viscous solution. The K value is 21.97; yield: 100%; SC: 39.8% (after 2 hours at 120° C. under reduced pressure).

Example 4

100 g of a 56% strength aqueous solution of polyethyleneimine (M_(w)=25 000) and 134.9 g of demineralized water are initially taken in a four-necked flask having an intensive stirrer and reflux condenser and are heated to an internal temperature of 75° C. with stirring. Air is passed in continuously in the process. When the temperature of 75° C. has been reached, a mixture of 65.61 g of acrylic acid and 11.19 g of methyl acrylate is added dropwise via a dropping funnel in the course of 2 hours. Thereafter, the experiment is stirred for a further 5 hours at 95° C. and then heated to 95° C. for about a further 3 hours. The product is a light orange, viscous solution. The K value is 19.1; SC: 42.0%; yield (acrylic acid): 90%; yield (methacrylate): 85%.

Example 5

100 g of a 56% strength aqueous solution of polyethyleneimine (M_(w)=25 000) and 134.9 g of demineralized water are initially taken in a four-necked flask having an intensive stirrer and reflux condenser and are heated to an internal temperature of 75° C. with stirring. Air is passed in continuously in the process. When the temperature of 75° C. has been reached, a mixture of 70.29 g of acrylic acid and 5.60 g of methyl acrylate is added dropwise via a dropping funnel in the course of 2 hours. Thereafter, the experiment is stirred for a further 5 hours at 95° C. and then heated to 95° C. for about a further 3 hours. A very viscous, clear, yellow solution forms. The K value is 17.3 (1% in H₂O); SC: 42.96% (after 2 hours at 120° C. under reduced pressure); yield (acrylic acid): 96%; yield (methacrylate): 99.5%.

Example 6

100 g of a 56% strength aqueous solution of polyethyleneimine (M_(w)=25 000) and 134.9 g of demineralized water are initially taken in a four-necked flask having an intensive stirrer and reflux condenser and are heated to an internal temperature of 75° C. with stirring. Air is passed in continuously in the process. When the temperature of 75° C. has been reached, 56.23 g of acrylic acid is added dropwise via a dropping funnel in the course of 90 min. Thereafter, 22.38 g of methyl acrylate are added dropwise in the course of 30 min. Thereafter, the experiment is stirred for a further 5 hours at 75° C. and then heated to an internal temperature of 95° C. for about a further 3 hours. A very viscous, clear, yellow solution forms. The K value is 16.2; SC: 41.4%. Yield (acrylic acid): 97%; yield (methacrylate): 97%.

Example 7

A polyamidoamine is prepared by condensation of adipic acid with diethylenetriamine according to the method stated in U.S. Pat. No. 4,144,123, Example 3, and then grafted in aqueous solution with an amount of ethyleneimine such that the polyamidoamine comprises 6.7 ethyleneimine units grafted on per basic nitrogen group. 321 g of a 62% strength aqueous solution of this polymer are initially taken in a four-necked flask having an intensive stirrer and reflux condenser, diluted with 479 g of demineralized water and heated to an internal temperature of 95° C. with stirring. Air is passed in continuously in the process. When the internal temperature of 95° C. has been reached, 87 g of acrylic acid are added dropwise in the course of 2 hours. Thereafter, the experiment is stirred for a further 6 hours at 95° C. The experiment is cooled to 80° C. and diluted with a further 200 ml of water. The product is a yellow, clear solution. K value: 21.2; SC: 32.6%; yield (acrylic acid): quantitative.

Example 8

430 g of polyethyleneimine (M_(w)=25 000) are initially taken in a four-necked flask having a water separator, gassed with nitrogen and heated to 80° C. with stirring. 600 g of acetic acid and 100 g of demineralized water are weighed into a dropping funnel and slowly added. Thereafter, the reaction mixture is heated slowly to an internal temperature of 160° C. and water/acetic acid are distilled off in the process. When the internal temperature is 160° C., the mixture is stirred for 1 hour 30 min at 160° C. Thereafter, final residues of water/acetic acid are removed under reduced pressure. The product is filled while hot into glass bottles.

Example 9

100 g of a 56% strength aqueous solution of polyethyleneimine (M_(w)=25 000) and 134.9 g of demineralized water are initially taken in a four-necked flask having an intensive stirrer and reflux condenser and are heated to an internal temperature of 55° C. with stirring. When the temperature of 55° C. has been reached, 13 g of epoxyhexane are added via a dropping funnel via a syringe in the course of 30 min. Air is now passed in. Thereafter, 65.6 g of acrylic acid are added via a dropping funnel in the course of 2 hours. The experiment is first stirred at 60° C. and subsequently heated to 90° C. After stirring for 12 hours, the reaction is complete. A very viscous, clear, red solution forms. SC: 43.58%; yield (acrylic acid): 99.3%.

Example 10

254.1 g of polyethyleneimine (M_(w)=25 000) are weighed into a 1 l four-necked flask having an intensive stirrer and reflux condenser, heated and stirred. In the course of 1 hour, 408.25 g of ethyl acetate are added dropwise and the temperature is then increased to 45° C. Thereafter, a slow temperature increase to 60° C. is effected. After 7 hours, ethyl acetate and ethanol are distilled off from the reaction mixture. The viscous product is again heated to 60° C. and 287.1 g of ethyl acetate are added. The experiment is now refluxed and kept under reflux for 8 hours 30 min. Ethyl acetate and ethanol are then distilled off.

Example 11

A polyamidoamine is prepared by condensation of adipic acid with diethylenetriamine by the method stated in U.S. Pat. No. 4,144,123, Example 3, and then grafted in an aqueous solution with an amount of ethyleneamine such that the polyamidoamine comprises 6.7 ethyleneimine units grafted on per basic nitrogen group. 362 g of 62% strength aqueous solution of the polyamidoamine are initially taken in a four-necked flask having an intensive stirrer and reflux condenser, diluted with 540 g of demineralized water and heated to an internal temperature of 95° C. with stirring. Air is passed in continuously in the process. When the internal temperature of 95° C. has been reached, 98.1 g of acrylic acid are added dropwise in the course of 2 hours. Thereafter, the experiment is stirred for a further 12 hours at 95° C. The experiment is cooled to 80° C. and diluted with a further 200 ml of water. The product is a viscous yellow solution. K value: 20.8; SC: 32.78%; yield (acrylic acid): 99.7%.

Example 12

750 g of a 56% strength aqueous solution of polyethyleneimine (M_(w)=25 000) are initially taken in a four-necked flask having an intensive stirrer and reflux condenser and are heated to an internal temperature of 95° C. with stirring. Air is passed in continuously in the process. When the internal temperature of 95° C. has been reached, 280.8 g of acrylic acid are added dropwise in the course of 2 hours. At the same time, 280.8 g of demineralized water are added dropwise in 2 hours. Thereafter, the experiment is stirred for a further 6 hours at 95° C. The experiment is cooled to 80° C. and diluted with a further 200 ml of water. The product is a yellow, clear solution. K value: 27.9; SC: 41.84%; yield (acrylic acid): 99%.

Example 13

355 g of a 56% strength aqueous solution of polyethyleneimine (M_(w)=25 000) and 178.4 g of demineralized water are initially taken in a four-necked flask having an intensive stirrer and reflux condenser and are heated to an internal temperature of 95° C. with stirring. Air is passed in continuously in the process. When the internal temperature of 95° C. has been reached, 166.6 g of acrylic acid are added dropwise in the course of 2 hours. Thereafter, the experiment is stirred for a further 6 hours at 95° C. The experiment is cooled to 80° C. and diluted with a further 200 ml of water. The product is a yellow, viscous solution. K value: 16.3; SC: 38.13%; yield (acrylic acid): 99%.

Example 14

425.8 g of a 56% strength aqueous solution of polyethyleneimine (M_(w)=25 000) and 525.6 g of demineralized water are initially taken in a four-necked flask having an intensive stirrer and reflux condenser and are heated to an internal temperature of 55° C. with stirring and introduction of nitrogen. Thereafter, 48.6 g of a 22.3% strength aqueous solution of a bisglycidyl ether of a polyethylene glycol having an average molar mass of 2000 are added dropwise in the course of 10 min. Thereafter, the temperature is increased to 95° C. while continuously passing in air, and 199.5 g of acrylic acid are added dropwise in the course of 2 hours. Thereafter, the experiment is stirred for a further 6 hours at 95° C. The product is an orange, viscous solution. The K value is 18.2; SC: 38.8%; yield (acrylic acid): 99.59%.

Example 15

A polyamidoamine is prepared by condensation of adipic acid with diethylenetriamine according to the method stated in U.S. Pat. No. 4,144,123, Example 3, and then grafted in aqueous solution with an amount of ethyleneimine such that the polyamidoamine comprises 6.7 ethyleneimine units grafted on per basic nitrogen group. This product is crosslinked by reaction with a bisglycidyl ether of a polyethylene glycol having an average molar mass of 2000 according to the data in Example 3 of U.S. Pat. No. 4,144,123. A polymer comprising ethyleneimine units and having a broad molar mass distribution (polydispersity of 400) is obtained. 800 g of a 24% strength aqueous solution of this stage are initially taken in a four-necked flask having an intensive stirrer and reflux condenser and are heated to an internal temperature of 95° C. with stirring. Air is passed in continuously in the process. When the temperature of 95° C. has been reached, 106.9 g of acrylic acid are added dropwise in the course of 2 hours. Thereafter, the experiment is stirred for a further 6 hours at 95° C. The product is a viscous, slightly turbid, orange solution. K value: 50.3; SC: 31.74%; yield (acrylic acid): 98%.

Examples 16 to 32

The following examples show the broad applicability of the functionalization reaction. The reactions were carried out in a 100 l stainless steel reactor. Polyethyleneimine is initially taken in the reactor and heated to 95° C. The reactants are added over a period of 2 hours with intensive stirring. The reaction mixture is then cooled to 25° C. and unreacted reactants are analyzed by headspace GC. In all cases, high conversions are achieved.

TABLE 1 PEI* Acrylic [parts by Addition 4- acid HEA 4-HBA Example weight] AA* HEA* HBA* [mg/kg] [mg/kg] [mg/kg] 16 67.5 7.50 0.00 0.00 37 <10 <10 17 67.5 6.75 0.75 0.00 30 <10 10 18 67.5 6.38 0.56 0.56 28 <10 <10 19 67.5 6.00 0.75 0.75 31 <10 <10 20 67.5 5.63 0.94 0.94 41 <10 <10 21 67.5 5.25 1.13 1.13 18 <10 <10 22 67.5 4.88 1.31 1.31 18 <10 <10 23 67.5 4.50 1.50 1.50 <10 11 <10 24 67.5 4.13 1.69 1.69 16 10 <10 25 67.5 3.74 1.88 1.88 14 17 <10 26 67.5 3.38 2.06 2.06 14 10 <10 27 67.5 3.00 2.25 2.25 12 11 <10 28 67.5 2.63 2.44 2.44 14 13 <10 29 67.5 2.25 2.63 2.63 13 12 <10 30 67.5 1.88 2.81 2.81 10 10 <10 31 67.5 1.5 3.00 3.00 10 10 <10 32 67.5 1.13 3.19 3.19 <10 13 <10 *PEI = polyethyleneimine, as 25% strength solution in water *AA = acrylic acid *HEA = hydroxyethyl acrylate *4-HBA = 4-hydroxybutyl acrylate

Examples 33 to 50 The Reactions are Carried Out as Described for Examples 16 to 32

TABLE 2 PEI [parts by Example weight] AA TBAM* AIPA* 33 67.5 7.5 0 0 34 67.5 6.75 0.75 0 35 67.5 6.75 0 0.75 36 67.5 6.375 0.563 0.563 37 67.5 6 0.75 0.75 38 67.5 5.625 0.938 0.938 39 67.5 5.25 1.125 1.125 40 67.5 4.875 1.313 1.313 41 67.5 4.5 1.5 1.5 42 67.5 4.125 1.688 1.688 43 67.5 3.75 1.875 1.875 44 67.5 3.375 2.063 2.063 45 67.5 3 2.25 2.25 46 67.5 2.625 2.438 2.438 47 67.5 2.25 2.265 2.265 48 67.5 1.875 2.813 2.813 49 67.5 1.5 3 3 50 67.5 1.125 3.188 3.188 *TBAM = N-tert-butylacrylamide, 20% by weight in THF *AIPA = acrylic acid isopropylamide, 20% by weight in water

Example 51

111.43 g of a 52.54% strength by weight aqueous solution of polyethyleneimine (M_(w)=25 000 g/mol, crosslinked with 4.55% of bisglycidyl ether of a polyethylene glycol having an average molecular weight of 2000 g/mol) and 201.4 g of demineralized water are initially taken in a four-necked flask with a high-intensity stirrer and reflux condenser and heated to 95° C. with stirring. During this procedure, air is passed in continuously. As soon as the temperature has reached 95° C., 73.54 g of 4-acryloylmorpholine are added dropwise over a period of 2 hours. Thereafter, stirring is effected for a further 6 hours at 95° C. and finally dilution is effected with 139.7 g of demineralized water. The product is an orange, viscous solution having a solids content of 25.57%.

Example 52

100 g of a 56% strength by weight aqueous solution of polyethyleneimine (M_(w)=25 000 g/mol, and 400 g of demineralized water are initially taken in a four-necked flask with a high-intensity stirrer and reflux condenser and heated to 95° C. with stirring. During this procedure, air is passed in continuously. As soon as the temperature has reached 95° C., 84.98 g of 2-acrylamidoglycolic acid are added dropwise over a period of 2 hours. At the same time, 100 g of demineralized water are added dropwise over a period of 2 hours. Thereafter, stirring is effected for a further 6 hours at 95° C. The product is a dark, red-brown, viscous solution having a solids content of 17.42%. The conversion is 100%.

Example 53

100 g of a 56% strength by weight solution of polyethyleneimine (M_(w)=25 000 g/mol, and 325.94 g of demineralized water are initially taken in a four-necked flask with a high-intensity stirrer and reflux condenser and heated to 95° C. with stirring. During this procedure, air is passed in continuously. As soon as the temperature has reached 95° C., 36.77 g of 4-acryloylmorpholine are added dropwise over a period of 2 hours with distribution. Stirring is then effected for a further 6 hours at 95° C. The product is a yellow solution having a solids content of 20.54%. The conversion is 100%.

Example 54

800 g of a 24% strength by weight aqueous solution of Lupasol® SK (M_(w)=2 million g/mol) are initially taken in a four-necked flask with high-intensity stirrer and reflux condenser and heated to 95° C. with stirring. During this procedure, air is passed in continuously. As soon as the temperature has reached 95° C., 106.92 g of acrylic acid are added dropwise over a period of 2 hours with distribution. Stirring is then effected for a further 6 hours at 95° C. The product is an orange, viscous solution having a solids content of 31.7%. The conversion is 100%.

Example 55

100 g of a 56% strength by weight solution of Lupasol® HF (M_(w)=25 000 g/mol) and 134.86 g of demineralized water are initially taken in a four-necked flask with high-intensity stirrer and reflux condenser and heated to 95° C. with stirring. During this procedure, air is passed in continuously. As soon as the temperature has reached 95° C., 56.23 g of acrylic acid are added dropwise over a period of 1 hour and distributed for 26 minutes and then 22.38 g of methyl acrylate are added in 34 minutes. Stirring is then effected for a further 6 hours at 95° C. The product is an orange, viscous solution having a solids content of 41.4%. The conversion is 100% and the K value is 16.2.

Example 56

7.5 parts of polyethyleneimine (M_(w)=25 000 g/mol) are added as a 50% strength by weight solution in water to 4 parts of water and heated to 45° C. 3 parts of a silver nitrate solution (500 g/l of silver nitrate in water) and then 4.1 parts of formic acid (55 g/l in water) or sodium borohydride solution (42 g/l in water) are added to the mixture. An orange solution and a white precipitate are formed. The UV-vis spectrum shows no absorption band in the range from 300 to 900 nm. Consequently, no stable silver nanoparticles have been formed.

Example 57

20 parts of the polymer solution from Example 6 were introduced into a glass reactor. 42 parts of a silver nitrate solution were added with stirring over a period of 10 minutes. The resulting white pasty mass was heated to 40° C. in the course of 30 minutes. 6 parts of 98% strength formic acid were then slowly added. Vigorous CO₂ evolution was observable in the process. After 24 hours, the reaction was complete and the reactor content was cooled to room temperature. The dark pasty mass at the bottom of the reactor was separated off by decanting. The product had a silver content of 43% by weight. The TEM analysis showed separate particles with silver crystallites on the surface of the polymer particles which were in contact with the reaction medium. A transmission electron micrograph is shown in FIG. 1.

Example 58

10 parts of the polymer solution from Example 14 were initially taken in a glass reactor. 20 parts of a silver nitrate solution were added with stirring in the course of 2 min. The solid white pasty mass obtained was heated to 40° C. in the course of 20 min. 3 parts of a 98% strength by weight formic acid were then slowly added with vigorous stirring. CO₂ evolution was observed in the process. After 2 hours, a further 30 parts of silver nitrate solution were added and then a further 4.5 parts of formic acid were slowly added. The reaction was continued for a further 16 hours. The reactor content was then cooled to room temperature. The dark pasty mass at the bottom of the reactor was isolated by decanting. The product had a silver content of 55% by weight and the supernatant solution comprised 38% by weight of silver. The TEM analysis showed separate particles with silver crystallites on the surface of the polymer particles which were in contact with the medium. Dilution of the pasty mass by a factor of 100 000 with water did not lead to precipitation of silver, which reflects the high colloidal stability of these polymer-silver particle complexes. The original UV-vis spectrum with a maximum at 410 nm and a small shoulder of 470 nm was retained. A transmission electron micrograph is shown in FIG. 2.

Example 59

In a glass reactor, 26.1 parts of silver oxide were suspended in 5 parts of the solution from Example 3. 3.5 parts of a 98% strength by weight formic acid were added in one portion. Vigorous gas evolution was observed and at the same time the reaction mixture acquired a dark color. Finally, the mixture was heated to 40° C. and left at this temperature for 30 minutes. The dark brown pasty mass isolated had, in the UV-vis spectrum, a peak at 410 nm which is characteristic of small silver nanoparticles.

Example 60

In a glass reactor, 4 parts of silver oxide and 1 part of silver nitrate solution are suspended in one part of the solution from Example 14. A further 4 parts of the polymer solution from Example 14 are added in two equal portions, a whiteish mixture being formed. This is heated at 40° C., and 1.5 parts of formic acid are added in 5 portions. After 2 hours, the reaction is complete and the mixture is cooled to room temperature. The dark brown pasty mass isolated has, in the UV-vis spectrum, a peak at 410 nm, which is characteristic of small silver nanoparticles.

Example 61

In a glass reactor, 1 part of the solution from Example 14 is diluted with 5 parts of water. A mixture of 4 parts of silver oxide and 1 part of silver nitrate is added and the mixture is heated to 40° C. 1.5 parts of formic acid are then added in 5 portions. Finally, a further 4 parts of the solution from Example 14 are added in two equal portions, a whiteish mixture being formed. This is heated to 40° C. After 2 hours, the reaction is complete. The dark solution obtained has a peak at 410 nm in the UV-vis spectrum.

Example 62

In a glass reactor, 1 part of the solution from Example 14 and 2 parts of water are mixed. 4 parts of silver oxide and 1 part of silver nitrate are added to the mixture. 1.5 parts of formic acid are then added in 5 portions. A further 4 parts of the solution from Example 14 are then added in two equal portions. A whiteish mixture is formed. This is heated to 40° C. After 2 hours, the reaction is complete. The dark solution obtained has a peak at 410 nm in the UV-vis spectrum.

Example 63

In a glass reactor, 1 part of the solution from Example 14 is heated to 40° C. 3.9 parts of silver acetate, followed by 1.5 parts of formic acid, are added. After a reaction time of 2 hours, the reaction is complete. A dark pasty mass having a silver content of 62% by weight is obtained. The UV-vis spectrum shows a maximum at 410 nm. A solution diluted by a factor of 100 000 with water gives the same spectrum.

Example 64

A solution of the pasty mass from Example 58, having a silver content of 2% by weight, is applied to a glass substrate by means of a knife coater and dried at room temperature or at 250° C. under reduced pressure. A 200 μm thick film is obtained. The film dried at room temperature can be redissolved in water. The film dried at 250° C. has an electrical resistance of 2 MΩ over a length of 4 cm. After treatment in air at 300° C. for 2 hours, a conductive film of sintered silver particles having a resistance of less than 1Ω over a length of 4 cm is obtained.

Examples 65 to 133 General Working Method Procedure A:

x parts of water and y parts of an aqueous silver nitrate solution (500 g/l) are introduced into a reactor. The mixture is shaken at 500 rpm and heated to a reaction temperature of 45° C. The polymer solutions from Examples 1 to 6, 9, 11 and 16 to 29 are added in one portion. In some cases, a white precipitate is formed. A stoichiometric amount, based on the metal content, of formic acid (51 g/l) is then added in one portion.

Procedure B:

As for procedure A but the formic acid is added in 40 equal portions, distributed uniformly over a period of 2 hours.

Procedure C:

As for procedure A but an aqueous formaldehyde solution having a concentration of 33 g/l is used.

Procedure D:

As for procedure B but with the use of the aqueous formaldehyde solution.

FIG. 3 shows a transmission electron micrograph of Example 74.

FIG. 4 shows a transmission electron micrograph of Example 84.

TABLE 3 Polymer UV-vis Max. solution from Polymer Silver Synthesis spectrum Dilution for particle Particle Example example [g/l] [g/l] procedure [nm] micrograph Absorption size [nm] size [nm] 65 16 20.2 51.2 A 402 1:1000 2.0 66 17 20.2 51.2 A 403 1:1000 1.3 67 18 20.2 51.2 A 403 1:1000 2.1 68 19 20.2 51.2 A 403 1:1000 2.1 69 20 20.2 51.2 A 402 1:1000 2.2 70 21 20.2 51.2 A 402 1:1000 1.2 71 22 20.2 51.2 A 402 1:1000 2.2 72 24 20.2 51.2 A 403 1:1000 1.8 73 25 20.2 51.2 A 402 1:1000 1.5 74 26 20.2 51.2 A 403 1:1000 1.6 75 27 20.2 51.2 A 403 1:1000 1.1 76 28 20.2 51.2 A 402 1:1000 2.1 77 29 20.2 51.2 A 403 1:1000 1.1 78 16 20.2 51.2 C 406 1:100 1.1 79 17 20.2 51.2 C 406 1:1000 1.5 80 18 20.2 51.2 C 409 1:1000 0.3 81 19 20.2 51.2 C 413 1:1000 0.2 83 20 20.2 51.2 C 413 1:1000 0.1 83 21 20.2 51.2 C 413 1:1000 0.2 84 22 20.2 51.2 C 406 1:1000 0.3 35 70 85 24 20.2 51.2 C 406 1:1000 0.5 20 30 86 25 20.2 51.2 C 406 1:1000 0.5 87 26 20.2 51.2 C 409 1:1000 0.3 65 140 88 27 20.2 51.2 C 406 1:1000 0.8 45 160 89 28 20.2 51.2 C 406 1:1000 0.7 90 29 20.2 51.2 C 406 1:1000 0.8 91 2 20.2 51.2 A 407 1:10 000 0.35 250 700 92 2 20.2 51.2 B 405 1:10 000 0.35 93 2 20.2 51.2 C 415 1:10 1.4 94 2 20.2 51.2 D 412 1:100 0.3 60/250 700 95 3 20.2 51.2 A 409 1:10 000 0.3 65 200 96 3 20.2 51.2 B 412 1:10 000 0.25 97 3 20.2 51.2 C 413 1:100 0.25 98 3 20.2 51.2 D 413 1:100 0.4 60 250 99 4 20.2 51.2 A 412 1:10 000 0.3 40 400 100 4 20.2 51.2 B 413 1:10 000 0.2 101 5 20.2 51.2 A 413 1:10 000 0.2 30/200 500 102 5 20.2 51.2 B 413 1:10 000 0.2 103 6 20.2 51.2 A 413 1:10 000 0.25 55 100 104 6 20.2 51.2 B 413 1:10 000 0.2 20 30 105 9 20.2 51.2 A 413 1:10 000 0.2 45 160 106 9 20.2 51.2 B 413 1:10 000 0.2 107 15 20.2 51.2 A 413 1:10 000 0.2 65 150 108 15 20.2 51.2 B 413 1:10 000 0.2 80 200 109 15 20.2 51.2 C 413 1:10 000 0.75 60 150 110 15 20.2 51.2 D 413 1:10 000 0.7 100 350 111 1 20.2 51.2 A 402 1:10 000 0.4 40 60 112 1 20.2 51.2 B 403 1:10 000 0.4 50 200 113 1 20.2 51.2 C 406 1:100 0.35 114 1 20.2 51.2 D 408 1:100 0.45 115 11 20.2 51.2 A 401 1:10 000 0.35 50 80 116 11 20.2 51.2 B 409 1:10 000 0.3 50 80 117 11 20.2 51.2 C 409 1:1000 0.25 30/200 30/400 118 11 20.2 51.2 D 405 1:1000 0.35 55 350 119 2 80.6 51.2 A 407 1:10 000 0.35 80 220 120 2 80.6 51.2 A 404 1:10 000 0.7 55 130 121 2 40.3 51.2 A 406 1:10 000 0.2 45 70 122 2 40.3 51.2 A 407 1:10 000 0.4 45 70 123 2 20.2 51.2 A 408 1:10 000 0.15 30 50 124 2 20.2 51.2 A 407 1:10 000 0.2 45 80 125 2 10.1 51.2 A 407 1:10 000 0.2 45 80 126 2 10.1 51.2 A 408 1:10 000 0.2 35 70 127 2 80.6 25.6 A 413 1:10 000 0.15 90 180 128 2 80.6 25.6 A 413 1:10 000 0.15 30/400 70/700 129 2 80.6 12.8 A 411 1:10 000 0.15 80 180 130 2 80.6 12.8 A 411 1:10 000 0.1 90 180 131 2 10.1 25.6 A 407 1:10 000 0.15 25 30 132 2 10.1 25.6 A 407 1:10 000 0.2 20/180 30/220 133 2 10.1 12.8 A 407 1:10 000 0.1 20/100 20/200 134 2 10.1 12.8 A 407 1:10 000 0.1 50 120

Examples 135 and 136

The product of Example 3 (7.5 parts) having a solids content of 50 g/l was heated to 45° C. 5 parts of a solution of potassium tetrachloropalladate (100 g/l) were added in one portion. A white precipitate forms, which slowly redissolved during the reaction. A solution of sodium borohydride in water (4.1 parts comprising 42 g/l of sodium borohydride) was then added. The reaction mixture was stirred for 4 hours, during which it assumed a black color. The TEM analysis showed the presence of metal nanoparticles. In a further batch (Example 98), the sodium borohydride solution was added in 4 portions. The result was the same. A transmission electron micrograph of the polymer particles is shown in FIG. 5. There, the polymer particles appear lighter gray and the metal nanoparticles darker gray on the surface of the polymer particles.

Examples 137 and 138

7.5 parts of the product from Example 3, having a solids content of 50 g/l, were heated to 45° C. 5 parts of a solution of potassium tetrachloroplatinate (200 g/l) were added in one portion. 4.1 parts of a solution of formaldehyde in water (33.4 WI) were then added. The reaction mixture was stirred for 4 hours, the solution acquiring a black color (Example 99). The TEM analysis shows the presence of metal nanoparticles. In a further batch (Example 100), a sodium borohydride solution was added in 4 portions. The results did not differ from one another. A transmission electron micrograph of the product obtained is shown in FIG. 6.

Examples 139 to 145

x parts of a residual solution of potassium chloroplatinate and 7.5 ml of an aqueous solution of the reaction product from Example 14 were introduced into a reactor. The mixture was stirred at 500 rpm and heated to the reaction temperature of 80° C. A stoichiometric amount, based on the metal content, of diethanolamine (166.6 g/l) was then added in one portion. The reaction mixture was left at 80° C. for 24 hours and stirred hourly for 5 minutes at 300 rpm. Finally, it was cooled to room temperature. Thereafter, x parts of potassium chloropalladate were added. The mixture was stirred at 500 rpm and heated to the reaction temperature of 70° C. A stoichiometric amount, based on the metal content, of 5-pentenoic acid (83.4 g/l) was then added in one portion. The resulting mixture was left at 70° C. for 24 hours and stirred hourly for 5 minutes at 300 rpm. Finally, it was cooled to room temperature.

A transmission electron micrograph of the product obtained is shown in FIG. 7.

Table 4 summarizes the batch sizes and the results of the TEM analysis.

TABLE 4 Polymer K₂PdCl₆ K₂PtCl₆ Diethanol- Pentenoic Particle (50 g/l) (100 g/l) (69.4 g/l) amine acid size Example [ml] [ml] [ml] [ml] [ml] [nm] 139 19.23 15.88 0.84 1.90 0.10 not anal. 140 19.23 13.37 3.35 1.60 0.40 not anal. 141 19.23 10.87 5.85 1.30 0.70  5-30 142 19.23 8.36 8.36 1.00 1.00 3-8 143 19.23 5.85 10.87 0.70 1.30 3-6 144 19.23 3.34 13.38 0.40 1.60 3-5 145 19.23 0.84 15.89 0.10 1.90 2-4

Examples 146 to 151

2.5 ml of a solution of tetraamineplatinum(II) nitrate (4.73% by weight of Pt) and 0.48 ml of polymer which has been diluted with demineralized water to a concentration of 10% by weight are initially taken in a reactor. The mixture is stirred at 500 rpm and heated to the reaction temperature of 85° C. 1.19 ml of pentenoic acid (having a concentration of 103.3 g/l) are then added in one portion. The reaction mixture is left for 24 hours at 85° C., stirring being effected hourly for 5 minutes at 300 rpm. Finally, cooling to room temperature is effected. The noble metal particles thus prepared have diameters of from 1 to 10 nm and high crystallinity.

TABLE 5 Reaction product Example from Example Color of the solution 146 52 light brown 147 53 yellow 148 51 yellow 149 55 yellow 150 54 yellow 151 52 yellow

Examples 152 to 156

0.1214 g of platinum acetylacetonate (98% strength) and 0.1070 g of palladium acetate (98% strength) are dissolved overnight in 7.54 g of diethylene glycol (99% strength). The solution is heated to 30° C. in a 50 ml flask together with a further 10 g of diethylene glycol. After 1 hour, polymer A is added and the mixture is then heated to 80° C. for 2 hours. After cooling to room temperature, the particle size distribution is determined by dynamic light scattering. The results are summarized in Table 6.

TABLE 6 Polymer A according to Example example Particle size [nm] 152 3 10 153 53 23 154 51 17 155 55 10 156 54 11 

1.-15. (canceled)
 16. A metal nanoparticle which is stabilized with derivatized polyethyleneimines or polyvinylamines, wherein the polyethyleneimines and polyvinylamines are any one or more selected from the group consisting of: A Homopolymers of ethyleneimine (aziridine); B Graft polymers of polyamidoamines with ethyleneimine; C Graft polymers of polyvinylamines with ethyleneimine; D Polymers of higher homologs of ethyleneimine; E At least partly hydrolyzed N-vinylcarboxamide homopolymers; and F At least partly hydrolyzed N-vinylcarboxamide copolymers, wherein the polyalkyleneimines and polyvinylamines are derivatized at the nitrogen atoms by reaction with alpha,beta-unsaturated carbonyl compounds by Michael addition.
 17. The metal nanoparticle of claim 16, wherein the alpha, beta-unsaturated carbonyl compound is any one or more selected from the group consisting of acrylic acid, acrylic acid esters, methacrylic acid, methacrylic acid esters, acrolein and acrylonitrile.
 18. The metal nanoparticle of claim 16, wherein a derivatized polyethyleneimine is employed, obtainable by reaction of a homopolymer of ethyleneimine with a diepoxide and/or bischlorohydrin ether and subsequent reaction with an alpha, beta-unsaturated carbonyl compound.
 19. The metal nanoparticle of claim 18, wherein the bischlorhydrin ether is 1,6-hexanediol ether or the bisglycidylether of a polyalkylene glycol.
 20. The metal nanoparticle of claim 18, wherein the alpha, beta-unsaturated carbonyl compound is selected from (meth)acrylic acid, alkyl(meth)acrylate and hydroxyalkyl(meth)acrylate.
 21. The metal nanoparticle of claim 16, wherein a derivatized polyethyleneimine is employed which is obtainable by reaction of a homopolymer of ethyleneimine with acrylic acid, hydroxyalkylacrylates and/or acrylamides.
 22. The metal nanoparticle of claim 16, wherein a derivatized polyethyleneimine is employed, which is obtainable by reaction of a graft polymer of polyamidoamine with ethyleneimine with acrylic acid.
 23. The metal nanoparticle of claim 22, wherein the graft polymer of polyamidoamine and ethyleneimine is first reacted with a diepoxide and/or bischlorohydrinether and subsequently with acrylic acid.
 24. The metal nanoparticle of claim 16, wherein the metal is any one or more selected from the group consisting of copper, silver gold, palladium, nickel, platinum, rhodium, iron, bismuth, iridium, ruthenium, rhenium, cobalt and osmium.
 25. A process for the preparation of metal nanoparticles of claim 16, in which a metal salt solution is reduced with a reducing agent in the presence of the derivatized polyethyleneimines or polyvinylamines.
 26. The process of claim 25, wherein metal salt solutions of two or more different metals are reduced simultaneously or in succession, metal nanoparticles comprising two or more different metals being obtained.
 27. The process of claim 25, wherein the reducing agent is any one or more selected from formic acid, formaldehyde, diethanolamine, 5-pentenoic acid, hydrazine, oxalic acid, sodium borohydride, ethanol, methanol, ethylene glycol and diethylene glycol.
 28. The process of claim 25, wherein silver as used in the form of silver oxide, silver acetate and/or silver nitrate.
 29. The process of claim 25, wherein the solvent used is water.
 30. The process of claim 25, wherein the solvent used is a polyhydric alcohol. 